Conventionally, research and development has been performed for reducing a size, a thickness, and a weight, and increasing functions of various electrical and electronic equipment. Particularly, in consumer products such as mobile phones, notebook computers, and digital cameras, there is a strong demand for the reduction in size, thickness, and a weight while increasing functions. Also, in various electrical and electronic equipment, a frequency and a speed of a transmission signal have been increased, and it is also required to prevent a corresponding increase in signal noise.
In order to meet such demands, a device embedded substrate having a structure in which various electrical and electronic devices, which have been conventionally mounted on a substrate surface, are embedded in an insulating base material that is an insulating layer of a substrate, and a device embedded multilayer circuit board obtained by laminating the device embedded substrates have been conventionally researched, developed, and manufactured as a circuit board incorporated in electrical and electronic equipment. For example, Patent Document 1 discloses a device embedded substrate and a manufacturing method thereof.
In the method for manufacturing a device embedded substrate disclosed in Patent Document 1, a conductive thin film layer made of a copper foil is formed on a support body, and an adhesive is applied onto the conductive thin film layer. Subsequently, an embedded device is mounted via the adhesive, and an insulating base material is then formed so as to cover the embedded device. In the device embedded substrate formed through manufacturing steps as described above, a thickness of the substrate itself is smaller than that of a conventional device embedded substrate, and more electrical and electronic devices can be embedded than those mounted on a substrate surface. Thus, the device embedded substrate can be used for electrical and electronic equipment for various purposes.